Majestic Mansions of Mighty Metahumans

While subterranean lairs in the mountains and satellite bases rotating high above the Earth have been in vogue for years, sometimes the simplest yet most elegant of backdrops for a headquarters is the most majestic. Take for instance Marvel's Avengers Mansion, in the heart of New York City, which stood for decades. Very classic and, aside from the occasional invasion from teams of villains, effectively guarded.

Earth-One's truly forgotten heroic team, the Doom Patrol, housed themselves in Niles Caulder's mansion in Midway City, home of the Hawkman and Hawkgirl. While that pair never seemed to meet up with the Patrol, inexplicably enough, the actual mansion could not have been all that far away from the museum where the alien couple was employed. And it was this fully equipped headquarters which kept Robotman, Negative Man, Elasti-Girl and Beast Boy safely secure. Well, until the team was lured to a small town by a disenfranchised former Nazi officer and led to their demise!

Earth-Two's most renowned heroic team, the Justice Society of America, moved to Gotham City during the 1960's wherein they purchased and remodeled their Brownstone. Equipped with state of the art technology, this location became the primary meeting place for the now seasoned team. although they did relocate temporarily to their old Civic City digs when charged with treason. This location, which they used during the 1940's and 1950's, was reused decades later when the Justice Society had been falsely accused of treason, while the Caulder Mansion was reused years later by Niles' widow Arani and her new Doom Patrol.

Another structure on Earth-One, the Hall of Justice used by the erstwhile Super Friends for  training teens,  A vast structure the size of a mansion, it mostly stored training equipment with a large meeting chamber and computer monitor, it existed in Gotham City as had the JSA Brownstone. 

Located in a seldom visited section of Gotham within a large forested park, much as the Society's HQ in Civic City had been.

Another location the Justice League used previously was a bunker compound within an industrial building owned by Hank Heywood, a site which the Justice Society visited on their own world when battling Ultra-Humanite's minions including members of Infinity Inc., who themselves traveled to the League's world to visit that bunker on one occasion.